Generally, a paper printed by an image forming apparatus such as an MFP (Multi-functional Peripheral) is discharged in such a manner that the printing surface thereof faces down and then stacked in a tray.
In a case of duplex printing, the paper is printed in an order from the second page to the first page, and is discharged in such a manner that a printing surface of which the page number is smaller faces down. However, for example, in a case in which a duplex printing of a document of 3 pages is carried out, a simplex printing is carried out in the last fraction page. If a simplex conveyance and simplex printing is carried out in the fraction page, the printing page numbers respectively corresponding to the front side and the back side of the paper are changed when compared with a case in which a duplex conveyance and duplex printing is carried out in the fraction page.
Conventionally, in order to consistent with the printing surface of the paper of the fraction page in the duplex printing, a duplex conveyance and simplex printing method has been carried out.
However, in the method described above, the printing surfaces corresponding to the front side and the back side of the paper are changed in both a case in which a simplex printing is designated initially and a case in which a duplex printing is designated. Thus, a printing processing may be carried out sometimes while the printing surface isn't kept at the same.